Hi, welcome to the forum!
That example you found, date +%Y%m%d_%H%M%S, is for Linux shells and will not work on Windows (unless using bash from git/msys, wsl or something).
On Windows there are different alternatives. See for example this: %DATE% and RClone
If you need more help then give us a bit more details: Do you want to run it from Command Prompt or PowerShell, manual as interactive command or from a scheduled task, etc. And if Command Prompt then locale date/time format is relevant, so share the output of echo %date% %time%.